Evidence for a Picritic, Volatile-rich Magma beneath Mt. Shasta, California |
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| Authors: | ANDERSON ALFRED T JR |
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| Institution: | Department of the Geophysical Sciences, The University of Chicago Chicago, Illinois 60637 |
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| Abstract: | Large, magnesium-rich olivines are plentiful in several Holocenecinder cones within 20 km of Mt. Shasta Summit. Glasses (formerlysilicate melts) included in the olivines are high alumina basalts(tholeiites and olivine tholeiites). In the most magnesian olivinesthe glass inclusions have large vapor bubbles. Surrounding someof the glass inclusions are broad Fe-rich zones and ghost outlines.These facts indicate crystallization of major proportions ofolivine from the initial trapped melts. The initial melts containedan inferred 24 per cent of MgO and were rich in volatiles. Theinferred entrapment temperature of the initial melt is 1410°C. The initial liquid is a possible mantle derived parentof Mt. Shasta basalts and andesites and of some hidden alpineperidotite. |
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